Messages in this thread | | | Subject | Re: [Bad page] trying to free locked page? (Re: [PATCH][RFC] fix kernel BUG at mm/migrate.c:719! in 2.6.26-rc5-mm3) | From | Lee Schermerhorn <> | Date | Tue, 17 Jun 2008 14:29:45 -0400 |
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On Tue, 2008-06-17 at 18:15 +0900, Daisuke Nishimura wrote: > On Tue, 17 Jun 2008 18:03:14 +0900, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote: > > On Tue, 17 Jun 2008 16:47:09 +0900 > > Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote: > > > > > On Tue, 17 Jun 2008 16:35:01 +0900, Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote: > > > > Hi. > > > > > > > > I got this bug while migrating pages only a few times > > > > via memory_migrate of cpuset. > > > > > > > > Unfortunately, even if this patch is applied, > > > > I got bad_page problem after hundreds times of page migration > > > > (I'll report it in another mail). > > > > But I believe something like this patch is needed anyway. > > > > > > > > > > I got bad_page after hundreds times of page migration. > > > It seems that a locked page is being freed.
I'm seeing *mlocked* pages [PG_mlocked] being freed now with my stress load, with just the "if(!page->mapping) { } clause removed, as proposed in your rfc patch in previous mail. Need to investigate this...
I'm not seeing *locked* pages [PG_lock], tho'. From your stack trace, it appears that migrate_page() left locked pages on the list of pages to be putback. The pages get locked and unlocked in unmap_and_move(). I haven't found a path [yet] where the page can be returned still locked. I think I need to duplicate the problem.
> > > > > Good catch, and I think your investigation in the last e-mail was correct. > > I'd like to dig this...but it seems some kind of big fix is necessary. > > Did this happen under page-migraion by cpuset-task-move test ? > > > Yes. > > I made 2 cpuset directories, run some processes in each cpusets, > and run a script like below infinitely to move tasks and migrate pages.
What processes/tests do you run in each cpuset?
> > --- > #!/bin/bash > > G1=$1 > G2=$2 > > move_task() > { > for pid in $1 > do > echo $pid >$2/tasks 2>/dev/null > done > } > > G1_TASK=`cat ${G1}/tasks` > G2_TASK=`cat ${G2}/tasks` > > move_task "${G1_TASK}" ${G2} & > move_task "${G2_TASK}" ${G1} & > > wait > --- > > I got this bad_page after running this script for about 600 times. >
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